It has been known for long that dental restorations can be favorably built from several layers, wherein, in most cases, the color of the inner layer is kept more intensely colored and more opaque and the outer layer comprises a translucent design in order to optically approach natural teeth.
Here, the inner layer also serves to mechanically stabilize the dental restoration which, particularly with bridges, has to absorb the sometimes considerable masticatory forces which arise.
An example of an early solution for such a dental bridge made of a metal base and a ceramic or plastic cover can be taken from EP 94 615 A1.
In the subsequent years, the multi-layer technique was optimized further. Thus, EP 781 530 A2 from the present applicant already shows a ceramic—instead of a metallic—reinforcement element as a reinforcement. Optionally, it can also be provided with an attachment for compensating for deviations in length of the bridge and allows for a veneering with a ceramic mass.
While solutions are used readily, in which the reinforcement or the reinforcement element consists of metal or ceramics and the veneer of plastic, bridges with ceramic reinforcement elements—which optionally also comprise an attachment—and a ceramic veneer are considered to be comparatively difficult to produce. Typically, the reinforcement element is produced initially, and subsequently the veneer is produced while taking careful account of the desired outer shapes.
As the production of the difference shape, so to speak, is not uncritical and as variations and exceeded tolerances cannot be excluded, the opposite approach has also been suggested, namely that an outer shape, a so-called prefacet, is produced in a pre-fabricated manner and that the inner shape is then provided subsequently to this.
This solution is possible with crowns and veneers, however, it presents further difficulties in terms of the production of dental bridges.